Method and apparatus for cracking oil



' July 25, 1933. c. R. EWING El AL METHOD AND APPARATUS FOR CRACKING OIL Filed March 21, 1929 Patented July 25, 1933 UNITED STATES P TENT.-

orrlcia- ,crmnLEs Jameson EWING, or TORONTO, ONTARIO, AND THOMAS M NTGQMERYQOF sennm, ONTARIO, CANADA, ASSIGNORS To STANDARD on. DEVELOPMENT com- PANY, A CORPORATION OF DELAWARE METHOD AND APPARATUS non CRACKING OIL Application filed March 21, 1929. Serial '.N0.' 348,'(08.

This invention relates to improvements in cracking hydrocarbon oils. A particular object of the invention is to provide improved methods and means for handling the cracked products so as to secure the desired characteristics in a plurality of separate fractions.

The invention will be fully understood from the following description, read in connection with the accompanying drawing, in

1Q which the figure is a diagrammatic sideelevation, partly in section, showing a pre ferred type of equipment. I

In the drawing, 1 denotes a cracking coil mounted in a furnace setting 2. This is 16 fired at 2a and the products of combustion escape through a stack, 2?). The coil discharges through a line 3 into an enlarged. thermally insulated reaction zone or soaking drum 4. A discharge line 5 leads .from the 2 upper part of the soakingdrum into the lower part of a separator 6. A pressurecontrol valve 7 is installed in line 5. Va-

' pors from the separatorpass through a line 8 into a vapor heat exchanger 9. A pressure 25 control valve 8' is placed in line 8. Condensate formed in the vapor heat exchanger flows through-a line 10 into a trap 11.

Condensate may be drawn off from the trap tlirougha line 12 which connects with 30 abranch line 134. A pump 14 in the latter line may be used to forward condensate into line 5, preferably not far from the release valve 7 on the low pressure side. A valve 15 is installed in line 12 between trap 11 and branch line 13. Fresh feed oil may be passed into branch line 13 through aline 16 which is regulated by a valve 17. Tar is drawn oil from the separator through a cooler 18 and is forwarded by a pump 19 to a storage tank, not shown. Some or all of the condensate formed in vapor heat exchanger 9 may overflow from trap 11 through a line 20 into an accumulator 21. Uncondensed vapors pass fromthis heat exchanger through a line 22 into a bottom compartment 23 of a rectifying column 24, which may be referred to as the primary tower. This compartment is set off from the bulkhead 23a.- Vapors pass'fromj comparttower 26.

"the upper rectifying section and the bottom compartment. I

inent 23 through a line 24a into a bottom compartment 25 of a secondary rectifying This has a bulkhead 25a, between Vapors pass from bottom compartment 25 through aline 27 into the rectifying section of tower 24. Vapors 7 pass overhead from tower 24 through line 28 into the lowerpart of the rectifying section of tower 26. Aline 26 connects accumulator 21 with a inid-portion-of tower 26. Vapors from tower 26 pass overhead through a line 29 through a vapor heat exchanger 30 to a cboler 3 1 and receiver32. The receiver has the usual gas vent 33 and draw-off line 34. 1 The latter line connects with a branch line 35 in which a pump 36 is; installed for forwarding distila late to the upper part'of tower 26.

. Liquid oil collecting in bottom compart-TIO mcnt 23 of tower 24 is drawn off through a.

Liquid oil collecting in thebottom of the rectifying section of tower 24 runs through a line 40 into bottom section 23 of that tower. It enters this above a bubble plate or equivalent device 41 therein. Vapors from line 22 enter'below this plate. A line 42 connects accumulator 21 with bottom compartment 23, pump 42 serving to transfer liquid from the bottom compartmentto the accumulator. Liquid oil collecting in 66mm compartment 25 of tower 26 is run through a line 43 to accumulator 21. Liquid oil collecting in the bottom part of the upper section of, tower.26 flows through a line 44 into bottom compartment 25. bubble plate 41'. is placed in this compartment between the vapor and liquid inlets.

Oil to be-cracked is passed into the system through a line 45 by pump 46.- Vapor heat exchanger 30 is provided with a by-pass47,

48 connected to line 45 and controlled by rectifying section ofrthe column-bye. tight valves :47, 48 and 49. Line 45-is connected to a coil section 50in the rear part of fur- 45 24 through line 39 if additional reflux is nace setting 2 which has a by-pass 51. Valves 52, 53 and 54 are provided to control the flow at this point in the system.

Coil section is connected to a line '55 which has branches 56 and 57 in vapor heat exchanger 9. Flow at this point is controlled by valves 58, 59 and 60. Line discharges into accumulator 21. The mixed fresh oil and condensates collecting in the accumulator flow. through a line 61, in which there is a pump 62, to the inlet of coil 1. Pressure control valves 24, 27 28, 29', are installed respectively in vapor lines 2401 27, 28 and 29 and liquid control valves 40 and 44 are installed respectively in lines 40 and 44. A valved by-pass 27a connects lines 24a and 27 In the operation of the system described, the cracking coil and soaking drum may be run under the standard conditions, for example, at a temperature approximating 750- 825 F. and a pressure approximating 300- 1000 pounds per square inch. Control valve 7 is set for a separator pressure of about 60 pounds per square inch. The quality of the tar'collecting in the separator is controlled by putting back the required amount of condensate through lines 12 and 13.

Important advantages are obtained by arranging the columns or bubble towers in two series-connected sections as shown. By so doing, it is possible to reboil the liquid oil collecting in lower compartment 25 of 26 by means of the hot vapors coming from lower compartment 23 of tower 24. Similarly, the liquid oil collecting in the lower part of the upper section of tower 24 is reboiled in bottom section 23 by the hot vapors entering through line 22. Plates 41 and 41' in these two compartments serve to give adequate vapor-liquid contact. From compartment 23 heavy gas oil is'taken off through line 39 and from the lower section of tower 26 light gas oil is taken off through line 39'. A portion of this may be put back into tower needed. By regulation of the pressure control and liquid control valves 24, 27. and 40, 44, the extent of reboiling and the gravity of the product may be readily adjusted. If too much reboiling is effected by passing the entire quantity of vapors through line 2%(1, a portion may be diverted through line 2 m. I

Preheat is efficiently and controllably supplied to the feedoil, without resort to high pressure heat exchange, by vapor heat exchangers 9 and30 and coil section 50.

The following example is given as illustrative of one way in which the invention may be practiced but we do notwish to limit ourselves to the particular conditions given:

When feeding to the cracking coil 1 10,000 United States gallons per hour of charging stock, half of which is fresh feed oil, we

prefer to maintain a coil outlet temperature of about 900 to 910 F. and to hold the pressure in the drum 4 at about 1000 pounds per square inch. The temperature of the tar collecting in the separator 6 is about 730 F. The vapors leave the heat exchanger 9 at around 700 F. and enter the lower compartment 23 of primary tower 24 at about that temperature. The vapors leave tower 24 at 550 F. and the liquid'refluxes through line 40 into compartment 23 at 570 F.

In the secondary tower 26, the reboiling of liquid oil is effected by means of vapors at around 680 F. passing through line 240: into the lower compartment 25 of tower 26. Vapors leave that tower through line 29 at 400 F. and liquid oil refluxes through line 44 into the lower compartment 25 at 500 F. The temperature of the vapors flowing through line 27, connecting compartment 25 and the upper part of tower 24, is about 630 F.

These figures are given for a method of operation in which the object is to obtain the maximum gasoline yield and are applicable when cracking reduced crude oils or gas oil. If ,in any case, the conditions require it, a head of oil may be maintained on the bulkheads 23a and 25a in towers 24 and 26 respectively and the oil so collecting may be stripped with steam. Ordinarily, this will be unnecessary.

While towers of the bell cap type have been shown, it will be understood that any equivalent form of rectification device may be used. Instead of pumpin back condensate for reflux to the towers, t e feed oil may be used as indirect heat exchange medium in the towers, as in common practice. Various other changes and alternative arrangements may be made within the scope of the appended claims in which it'is our intention to claim all novelty inherent in the invention as broadly as the prior art permits.

We claim:

1. In combination with a source of hydro carbon vapors at high temperature, a primary rectifying column, a first compartment at the base thereof and out of vapor contact with the upper portion of the column, a secondary rectifying column, a second compartment at the base thereof and out of vapor contact with the upper portion of the column, means for passing the vapors in series through the compartments, means for passing vapors from the second compartment to the primary rectifying column, a vapor line between the rectifying columns, and means for returning liquid hydrocarbons collecting in each column to the compartment at the base of the column.

2. In combination with means for crackits base, means for passing the vaporous product from the cracking system into the closed compartment of the first tower, means for passing residual vapors from said compartment into the closed compartment of the second tower,.means for passing the vapors from the second compartment into the upper portion of the first tower, and means for' passing liquid from the upper portion of the first tower into the bottom compartment,

in a first and then in 'a second rectifying.

zone'out of vapor contact with the reboiling zones returning condensate from the first rectifying zone into the first reboiling zone and from the second rectifying zone' into the second reboiling zone in direct contact with the vapor in said reboiling zones I to reboil said condensates by the heat content of the vapors, withdrawingreboiled condensate, and passing it to the cracking operation.

4. In the rectification of a hydrocarbon distillate, the improvement which comprises passing it substantially in vapor form through a series of liquid oil reboiling zones, .then through the same number of corresponding rectifying zones in the same succession, said rectifying zones being out of vapor contact with the reboiling zones, supplying to each of the reboilin zones liquid oil formed by condensation o vapors pass ing through the corresponding rectifying zone, directly contacting the liquid and vapor in the reboiling zone to reboil the liquid by the heat content of the vapor, and removing liquid from each reboiling zone and uncondensed vapor from the last rectifying zone.

CHARLES RINGGOLD EWI-NG. THOMAS MONTGOMERY. 

